The invention relates to a golf club head. More particularly, the invention is related to a golf club head with a multi-radius face.
The design of club heads has long been studied. Among the more prominent considerations in club head design are loft, lie, face angle, horizontal face bulge, vertical face roll, face progression, sole curvature, center of gravity location, and overall head weight. Although all of these aspects may be considered in golf club engineering, several are often accorded more weight in the design process due to their significant impact on club performance.
The shape and sizing of a club face is quite complex. Of particular interest in club head design are two characteristics of the face, the horizontal face bulge and the vertical face roll. Horizontal face bulge radius is measured from the heel to toe or along the horizontal plane of the face, and is important because it compensates for a golfer""s hitting of the ball off of the centerline of the face. If a ball is hit at an off-center location, the bulge effectively compensates for this misalignment that would otherwise cause hooking or slicing. A typical wood has a horizontal face bulge radius of between 8 and 16 inches.
Vertical face roll radius is measured from the top of the face to the bottom of the face in a vertical position, and this factor affects the trajectory of the ball off the face. A typical wood has a vertical face roll radius of between 12 and 18 inches.
The presence of bulge and roll radius, and the degree of radius applied to the face, are critical to the performance of the club. As perfection in the golf swing is not attained by most golfers, off-center hits are common. Yet, proper club head design, particularly with respect to the face geometry, can help compensate for the imperfect swing. There are trade-offs, however, in setting the face geometry. Too much horizontal face bulge, for example, can lead to poor directional control. In addition, club heads having too much vertical face roll can detrimentally exacerbate the trajectory of the ball upon impact.
Typically, golf clubs are designed with a single bulge. However, some club heads have been designed with multiple bulge radii. U.S. Pat. No. 6,093,115 discloses a golf club head having an asymmetric ball striking face such that one side of the face, as measured from the center of the face, has a first bulge radius and the other side of the face has a second bulge radius. One of the heel portion and the toe portion of the ball striking face has a bulge radius of 8 inches, while the other has a bulge radius of 24 inches. U.S. Pat. No. 5,415,405 discloses a hitting surface of a golf club head that is divided into three adjacent portions, each portion forming an arc of a circle with a different radius. The radii of the various portions range between 7 and 20 inches.
Japanese Publication 11042301 discloses a golf club head with three different bulge radii. The central part of the club face has a bulge radius that is greater than that of either adjacent part, with the difference in bulge radii ranging from about 1.27 to 2.95 inches.
Golf clubs are also typically designed with a single roll radius. However, some club heads have been contemplated to include multiple roll radii. For example, U.S. Pat. No. 4,162,074 discloses a putter with a face that forms a convex striking surface. The surface is generally parabolic or exponential, and thus does not have a constant roll radius.
Moreover, U.S. Pat. No. 4,508,349 discloses a golf club with a striking face that has a central portion with accentuated roll. The central roll portion has a radius of curvature between 0.70 and 1 inch. Grooves extend parallel to the accentuated roll portion on opposite sides thereof, while flat surfaces extend along the striking face above and below the upper and lower grooves respectively. The design is claimed to provide for increased compression of the golf ball resulting in an unexpectedly long drive.
Despite the several aforementioned club head designs, there remains a need for a wood-type golf club with a club face designed to optimize launch conditions for various ball impact locations on the face. In particular, there remains a need for a golf club face with dual roll radii. Such a golf club design allows for improvement in performance such that ball launch conditions degrade less as the impact point of the ball departs from the center of the club face. In addition, there remains a need for a golf club face combining multiple bulge radii with multiple roll radii.
The present invention relates to a metal wood golf club head adapted for attachment to a shaft. The head includes a shell defining an inner cavity and further including a face. The face has at least two roll radii disposed adjacent each other and defined about a horizontal line proximate the center of the face, with a first roll radius above the line and a second roll radius below the line. Preferably, the first roll radius is smaller than the second roll radius. The first roll radius may be less than about seventy percent of the second roll radius. The first roll radius may be between about 4 inches and about 12 inches, and the second roll radius may be between about 8 inches and about 16 inches. In a preferred embodiment, the first roll radius is about 6 inches, and the second roll radius is about 10 inches.
The present invention also relates to a metal wood golf club head adapted for attachment to a shaft, including a shell defining an inner cavity and further including a face. The face has at least two roll radii disposed adjacent each other and defined about an alignment line on the face that extends from the heel end to the toe end. Preferably, a first roll radius above the alignment line is smaller than a second roll radius below the alignment line. A first roll radius above the alignment line may be less than about seventy percent of a second roll radius below the alignment line.
In another embodiment of a metal wood golf club head, the face has at least two roll radii and at least two bulge radii. The roll radii are disposed adjacent each other and defined about an alignment line on the face extending from the heel end to the toe end. Preferably, the face includes a first roll radius above the alignment line and a second roll radius below the alignment line, with the first roll radius being smaller than the second roll radius.
The present invention further relates to a metal wood golf club head adapted for attachment to a shaft. The head includes a shell defining an inner cavity and further including a face. The face has vertical and horizontal center lines proximate its center. The face also has a toe-side alignment line parallel to the vertical center line and disposed about half-way between a toe region of the shell and the vertical alignment line, and a heel-side alignment line parallel to the vertical center line and disposed about half-way between a heel region of the shell and the vertical alignment line. The face has a central region with a first bulge radius between the toe-side and heel-side alignment lines, and peripheral regions adjacent the central region. The first bulge radius of the central region of the face is substantially larger than the bulge radius of the peripheral regions of the face. In one embodiment, the bulge radius of the peripheral regions of the face is about 10% to about 40% smaller than the first bulge radius.
In addition, the present invention relates to a method of forming a metal wood golf club head, comprising the steps of: forming a shell defining an inner cavity and further including a face having a horizontal center line that extends from a heel end to a toe end, the horizontal center line defining an upper portion and a lower portion, and forming the upper portion of the face with a roll radius that is smaller than a roll radius of the lower portion of the face. The method may further include the step of forming substantially the entire upper portion of the face with a first roll radius, and forming substantially the entire lower portion of the face with a second roll radius. The face additionally may be formed with at least two bulge radii disposed about a vertical center line that extends from a crown region to a sole region, the vertical center line defining a proximal portion having a first bulge radius and a distal portion having a second bulge radius.